I don't know how all of this will play out, but the problem is that for most universities, the education of home/EU students is cross-subsidised by other things.
Education and buildings and facilities are subsidised by the money made on summer courses and conferences using the halls when students aren't there - that income is gone this year.
Home/EU students are subsidised by international students - a lot of that income will be gone if international students don't want to, or can't, come.
Some of the cheapest-to-run arts subjects subsidise the science teaching - if there are fewer students coming for arts courses or universities reduce their fees for these courses, then they might have to close the most expensive degrees.
There's not much saving in teaching online, because the staff are doing all the same work anyway - sometimes more, if they're being asked to prepare for both in-person and online teaching or they need to teach more courses (because most unis have now started a hiring freeze and there are staffing gaps).
I don't know what the solution is, tbh.